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36 lines
766 B
C++
36 lines
766 B
C++
// $Id$
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#include "mathlib/ssemath.h"
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__m128 PowSSE_FixedPoint_Exponent(__m128 x, int exponent)
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{
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__m128 rslt=Four_Ones; // x^0=1.0
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int xp=abs(exponent);
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if (xp & 3) // fraction present?
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{
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__m128 sq_rt=_mm_sqrt_ps(x);
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if (xp & 1) // .25?
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rslt=_mm_sqrt_ps(sq_rt); // x^.25
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if (xp & 2)
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rslt=_mm_mul_ps(rslt,sq_rt);
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}
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xp>>=2; // strip fraction
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__m128 curpower=x; // curpower iterates through x,x^2,x^4,x^8,x^16...
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while(1)
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{
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if (xp & 1)
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rslt=_mm_mul_ps(rslt,curpower);
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xp>>=1;
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if (xp)
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curpower=_mm_mul_ps(curpower,curpower);
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else
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break;
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}
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if (exponent<0)
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return _mm_rcp_ps(rslt); // pow(x,-b)=1/pow(x,b)
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else
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return rslt;
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}
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